Absorbent article comprising an elastic web material

ABSTRACT

A pant type absorbent article such as a pant diaper, a sanitary pant or incontinence pant, said article having a core region ( 3 ) comprising an absorbent core ( 2 ) and a chassis region ( 4 ) surrounding the core region. The chassis comprises front, back and waist regions ( 5, 6  and  7 ). The article in at least a part of the chassis region ( 4 ) comprises an outer coversheet ( 10 ) in the form of an elastic web material ( 11 ) constituting the sole component of the chassis ( 4 ) in at least 20% of the total surface area of the article ( 1 ), said elastic laminate having an opacity of at least 40% and a basis weight of no more than 100 g/m 2 .

TECHNICAL FIELD

The present invention refers to a pant type absorbent article such as apant diaper, a sanitary pant or incontinence garment, said articlecomprising an elastic web material.

BACKGROUND OF THE INVENTION

Absorbent articles having defined core regions and chassis regions aresupposed to have a comfortable fit about the wearer. For pant articleslike pant diapers, sanitary pants and incontinence pants it is alsodesirable that the articles are capable of being pulled up and down overthe hips of the wearer to allow the wearer or caregiver to easily put onand remove the article when it has been soiled. It is known to make suchabsorbent pants with elasticized stretchable side panels and waistportion, usually comprising elastic members, such as elastic threads,contractably affixed between the backsheet and the topsheet.

It is further known to make portions of the chassis of absorbentarticles of an elastic material, such as stretch-bonded laminates. Suchlaminates may include a layer of meltblown elastomeric fibers which havebeen stretched and sandwiched between outer layers of spunbonded webs.

U.S. Pat. No. 6,552,245 discloses an extensible outer cover for anabsorbent article which provides a certain permanent deformation whensubjected to a tensile force. The extensible outer cover comprises anecked laminate in the form of one layer of a necked non-elastic filmand one layer of an elastic film. The films may be breathable.

WO 03/047488 discloses an elastic laminate comprising an elastic filmwhich on opposite sides is bonded to first and second non-elasticfibrous layers. The laminate is made by bonding the non-elastic fibrouslayers to the elastic film layer and subsequently stretching thecomposite material, causing the non-elastic materials to break. Theelastic film material may be of a breathable material. The laminate maybe incorporated in an absorbent article.

US2003/0022582 describes a laminate in which an elastomeric film isbound between two or more layers of nonwoven webs. The laminate is saidto be particularly useful in elastic diaper “ears” that can be stretchedto accommodate variously sized wearers.

Further examples of absorbent articles which in part are made of elasticlaminates are found in U.S. Pat. No. 6,476,289 and JP 10043235.

WO03/19714 discloses a polymeric multilayer film having a highpercentage of fillers. U.S. Pat. No. 4,698,261 describes an opaquepolyolefin film comprising five layers which is advantageously used forpackaging purposes. WO99/32164 describes disposable absorbent articlescomprising a microporous backsheet upon which graphics can be printed.The backsheet of WO99/32164 is advantageously whitened with additives.

International applications PCT/SE2004/001004 and PCT/SE2004/001005 referto absorbent articles comprising an outer coversheet in the form of anelastic laminate having improved cloth-like feel and punctureresistance.

There is however still room for improvement with respect to theproperties of absorbent articles comprising an elastic web material, forexample an elastic laminate, as an outer coversheet, particularly theircloth-like appearance. The comfort, fit and soft feel of absorbentarticles of the above mentioned type is also important. The cost aspectis further important for disposable articles, which are discarded afterone single use.

OBJECT AND MOST IMPORTANT FEATURES OF THE INVENTION

The object of the present invention is to provide an absorbent articlehaving a core region and a chassis region and which combines propertiesof comfort and fit to the wearer's body and a soft and cloth-likeappearance and feel close to textile materials.

The article according to the invention has a core region comprising anabsorbent core and a chassis region surrounding the core region, saidchassis region comprising front, back and waist regions, while the coreregion is located at least in the crotch portion of the article, aliquid impermeable backsheet is arranged at least in the core region onthe garment facing side of the absorbent core and a liquid permeabletopsheet is arranged at least in the core region on the wearer-facingside of the absorbent core. In at least a part of the chassis region thearticle comprises an outer coversheet in the form of an elastic webmaterial constituting the sole component of the chassis in at least 20%of the total surface area of the article, said elastic web materialhaving an opacity of at least 40% and a basis weight of no more than 100g/m².

Preferably the elastic web material has an opacity of at least 50%, morepreferably at least 60%.

In one embodiment the elastic web material is a laminate composed offirst and second layers of fibrous material and an elastic film layerlocated between said first and second fibrous layers,

In one aspect of the invention the elastic film contains an opacifyingfiller.

According to one embodiment the opacifying filler is an organic orinorganic dye, a coloring agent or a whitening agent. Materials such astitanium dioxide, inorganic carbonates, synthetic carbonates, talc,nepheline syenite, magnesium hydroxide, aluminium trihydratesiatomaceous earth, mica, natural or synthetic silicas, calcinated claysand mixtures thereof are examples of suitable opacifying fillers.

In one embodiment, both layers of fibrous material of the elasticlaminate have an elongation at maximum load greater than the elasticityof the elastic laminate.

Characteristically, the layers of fibrous material have an elongation atmaximum load of at least 10%, preferably at least 20% greater than theelasticity of the elastic laminate.

In a further embodiment the elastic film layer is breathable.

In one aspect of the invention the elastic laminate has a Water VapourTransmission Rate according to ASTM E96-00 Procedure D of at least 1500g/m² 24 h, preferably at least 3000 g/m² 24 h.

In yet a further embodiment, the first and/or the second layers offibrous material comprise a mixture of polypropylene and polyethylenepolymers.

According to one embodiment said elastic laminate comprises first andsecond fibrous layers of spunbond material, each having a basis weightof between 10 and 35 g/m², preferably between 12 and 30 g/m², morepreferably between 10 and 25 g/m², and a breathable elastic film layerhaving a basis weight between 20 and 80 g/m², preferably between 20 and60 g/m², said elastic laminate having a Water Vapour Transmission Rateaccording to ASTM E96-00 Procedure D of at least 1500 g/m² 24 h,preferably at least 3000 g/m² 24 h.

According to a further embodiment said elastic web material has anelasticity in the transverse direction of the article of at least 30%,preferably at least 50%, more preferably at least 70%, when measuredaccording to the elasticity test specified in the description.

In one aspect of the invention the elastic web material has a basisweight of no more than 90 g/m².

In a further aspect the elastic web material has an opacity (%)/basisweight (g/m²) ratio of at least 0.4, preferably at least 0.5 and morepreferably at least 0.6.

According to a further embodiment the elastic web material constitutesthe sole component of the chassis in at least 25%, preferably at least30%, more preferably at least 40%, of the surface area of the article.

In one aspect of the invention said elastic web material has a Softness(5) according to Kawabata of at least 20, preferably at least 30 andmore preferably at least 40.

According to one embodiment said elastic web material has a Formability(F) according to Kawabata of no more than 50, preferably no more than30, more preferably no more than 20 and most preferably no more than 10.

In a further embodiment said elastic web material has a Drapability (D)according to Kawabata of no more than 40.

According to a further embodiment a substantial part of the crotchportion of the article is free from said elastic web material.

For certain applications it is preferred that the waist region of thechassis region is free from said elastic web material.

According to one embodiment the surface area of the absorbent coreamounts to no more than 30%, preferably not more than 20%, of the totalsurface area of the article, as measured in a flat state of the article.The term “flat state” herein means in an opened untensioned state, asseen in FIG. 2 of the drawings, and in which any tensioned elasticmembers have been deactivated.

In one embodiment of the invention the elastic web material constitutesboth the outer and the inner coversheet of the article in at least apart of the chassis region.

In a further aspect of the invention the article is a pull-up pantproduct comprising an elastic waist region, which is free from saidelastic web material, a crotch portion which is also free from saidelastic web material and wherein the elastic web material is arranged asthe sole component in at least a substantial part of the front region ofthe article, which in use is intended to be applied over the stomach ofthe wearer. The term “a substantial part” herein means at least 50% ofthe surface area of the front region.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a perspective view of a pant diaper.

FIG. 2 shows is a simplified plan view of the pant diaper in its flat,uncontracted state prior to formation as seen from the body facing side.

FIG. 3 is a cross section according to the line III-III in FIG. 2.

FIG. 4 is a cross section through an elastic laminate according to theinvention according to the line IV-IV in FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS

The invention will in the following be closer described with referenceto some embodiments shown in the accompanying drawings.

Absorbent Article

The term “absorbent article” refers to products that are placed againstthe skin of the wearer to absorb and contain body exudates, like urine,faeces and menstrual fluid. The invention mainly refers to disposableabsorbent articles, which means articles that are not intended to belaundered or otherwise restored or reused as an absorbent article afteruse. According to the invention pant type absorbent articles arereferred to having a core region and a chassis region surrounding thecore region. Examples of such pant type absorbent articles are pantdiapers, sanitary pants and incontinence pants.

The drawings show an embodiment of a pant diaper 1 for an infant or anincontinent adult. Said pant diaper typically comprises an absorbentcore 2 located in a core region 3 of the article, and a chassis 4surrounding the core region. The chassis comprises front 5, back 6 andwaist regions 7. The core region 3 is located at least in the crotchportion 19 of the article and extends a certain distance into the front5 and back regions 6. The crotch portion 19 is herewith defined as thenarrow part of the article intended to be worn in the wearer's crotchbetween the legs.

The article has a longitudinal direction y and a transverse direction x.

The article comprises a liquid permeable topsheet 8 and a liquidimpermeable backsheet 9 covering at least the core region 3. Theabsorbent core 2 is enclosed between the topsheet and the backsheet.

Topsheet

The liquid permeable topsheet 8 can consist of a nonwoven material, e gspunbond, meltblown, carded, hydroentangled, wetlaid etc. Suitablenonwoven materials can be composed of natural fibers, such as woodpulpor cotton fibres, manmade fibres, such as polyester, polyethylene,polypropylene, viscose etc. or from a mixture of natural and manmadefibres. The topsheet material may further be composed of tow fibres,which may be bonded to each other in a bonding pattern, as e.g.disclosed in EP-A-1 035 818. Further examples of topsheet materials areporous foams, apertured plastic films etc. The materials suited astopsheet materials should be soft and non-irritating to the skin andintended to be readily penetrated by body fluid, e.g. urine or menstrualfluid. The topsheet may be different in different parts of the absorbentarticle.

Backsheet

The liquid impervious backsheet 9 covering the core region 3 on thegarment-facing side of the core is of a liquid impervious material, suchas a thin plastic film, e.g. a polyethylene or polypropylene film, anonwoven material coated with a liquid impervious material, ahydrophobic nonwoven material, which resists liquid penetration or alaminate comprising plastic films and nonwoven materials. The coreregion backsheet material 9 may be breathable so as to allow vapour toescape from the absorbent core, while still preventing liquids frompassing therethrough. Examples of breathable backsheet materials areporous polymeric films, nonwoven laminates from spunbond and meltblownlayers, laminates from porous polymeric films and nonwovens. Thebacksheet 9 is preferably inelastic.

Outer Coversheet

The outer coversheet 10 covering the front and back regions 5 and 6 ofthe chassis 4 comprises an elastic web material 11 having a basis weightof no more than 100 g/m². The elastic web material is elastic at leastin the transverse x-direction of the article. The elasticity in thex-direction should be at least 30%, preferably at least 50%, morepreferably at least 70%, as measured by the elasticity test specifiedbelow.

Preferably the elastic web material is elastic also in the y-directionof the article. However the elasticity in the y-direction is preferablylower than in the x-direction. The elasticity in the y-direction shouldin be at least 20%.

In the embodiment shown and described below the elastic web material isan elastic laminate 11 is composed of first and second outer layers offibrous material 12 a and 12 b and a middle elastic film layer 13located between said fibrous layers. However it is understood that othertypes of elastic web materials may be used, such as elastic nonwovenmaterials, nonwoven materials which per se are inelastic, but which havebeen elastified by means of elastic threads etc. The elastic webmaterials may comprise one layer or two or more layers that have beenlaminated.

In the elastic laminate shown and described below it is preferred thatthe outer fibrous layers 12 a and 12 b are chosen so that they, incombination with the inner elastic film layer, give the material highresistance to puncture. They also provide a soft and cloth-like feel tothe laminate. Examples of suitable materials are carded webs andspunbond materials. The basis weight of the fibrous material layersshould be between 10 and 35 g/m², preferably between 12 and 30 g/m²,more preferably between 15 and 25 g/m². Examples of suitable polymersused in the fibrous materials are polyethylene, polyesters,polypropylene and other polyolefin homopolymers and copolymers. Naturalfibres, for example cotton, may also be used as long as they provide therequired properties. A mixture of polymers can contribute to a higherflexibility of the nonwoven layer, and through this, give the nonwovenmaterial a higher elongation at maximum load. A mixture of polyethyleneand polypropylene polymers has proved to provide good results in thisrespect. A mixture of fibers of different polymers is also possible.

The middle layer is according to one embodiment of the invention anapertured elastic film having a basis weight between 20 and 80 g/m²,preferably between 20 and 60 g/m². The film may be of any suitableelastic polymer, natural or synthetic. Some examples of suitablematerials for the elastic film are low crystallinity polyethylenes,metallocene-catalyzed low crystallinity polyethylene, ethylene vinylacetate copolymers (EVA), polyurethane, polyisoprene, butadiene-styrenecopolymers, styrene block copolymers, such as styrene/isoprene/styrene(SIS), styrene/butadiene/styrene (SBS), orstyrene/ethylene-butadiene/styrene block copolymer. Blends of thesepolymers may also be used as well as other modifying elastomeric ornon-elastomeric materials. One example of a suitable film is anapertured three-layer elastomeric film of PE-SEBS-PE.

The total basis weight of the laminate is preferably 100 g/m² or less,more preferably no more than 90 g/m².

The elastic laminate 11 may be manufactured according to the methoddisclosed in WO 03/047488, wherein one spunbond layer 12 a is applied tothe film 13 in a tacky state and will thus bond to the film layer, whilethe other spunbond layer 12 b is adhesively laminated to the film layer13, using for example a pressure sensitive hot melt adhesive.Alternatively the laminate is manufactured according to a modifiedversion of this known method, wherein the modification involves that thelaminate is incrementally stretched (through intermeshing gears, IMG),to a point below the elongation at peak load of at least one of thenon-elastic nonwoven layers to retain some strength for at least one ofthe nonwoven layers. The other layer may also be stretched to a pointbelow its elongation at peak load, or to a point at which it will tearduring stretching.

The method disclosed in WO 03/047488 involves stretching of the laminateabove the point of failure of the fibrous material, so that thenon-elastic layers break completely. Therefore, as described in WO03/047488, the elongation of the laminate is not limited by the stretchmodulus of the non-elastic material.

According to the modified method at least one, preferably both fibrouslayers, which are bound to the elastic film are not, in contrast to themethod described in WO 03/047488, completely torn upon manufacture of alaminate according to the present invention. Selection of fibrousmaterials which have an elongation at maximum load greater than theelasticity of the elastic laminate allows the elastic film to stretchwithout being hindered by the fibrous layers. Such a selection alsoensures that the fibrous layers contribute to the puncture resistance ofthe laminate, as they are not completely torn or broken duringmanufacture. Preferably the fibrous layers, or at least one of thefibrous layers have an elongation at maximum load that is at least 10%higher than the elasticity of the laminate. This is described in moredetail in PCT/SE2004/001005, which is incorporated herein by reference.

The opacity of a material layer is the characteristic ability of thematerial layer to visually hide from view an underlying object orpattern. The opacity is measured in %, wherein 100% opacity means thatnothing can be seen through the material layer and 0% means that thematerial layer is completely transparent. The opacity is measured by theOpacity Test described below, which is based onluminous-reflectance-factor data.

Opacity of the laminate can be obtained by the incorporation ofopacifying fillers into the laminate, particularly into the elasticfilm. Such pigments can be organic or inorganic dyes, colouring agents,or whitening agents. Inorganic materials such as titanium dioxide,inorganic carbonates, synthetic carbonates, talc, nepheline syenite,magnesium hydroxide, aluminium trihydrate siatomaceous earth, mica,natural or synthetic silicas, calcinated clays and mixtures thereof arepreferred examples of opacifying fillers.

The filler is preferably added as a master batch at the extrusion of thefilm. One example of an appropriate concentration is about 5% filler byweight of the film.

It is further preferred that the elastic laminate 11 has a breathability(Water Vapour Transmission Rate) according to ASTM E96-00 Procedure D ofat least 1500 g/m² 24 h, preferably at least 3000 g/m² 24 h.

The open area of the elastic film layer is preferably at least 5%, morepreferably at least 8%. The open area is measured by image analysismethods and is defined as the sum of the hole area divided by the totalarea of the film sample.

Absorbent Core

The absorbent core 2 can be of any conventional kind. Examples ofcommonly occurring absorbent materials are cellulosic fluff pulp, tissuelayers, highly absorbent polymers (so called superabsorbents), absorbentfoam materials, absorbent nonwoven materials or the like. It is commonto combine cellulosic fluff pulp with superabsorbents in an absorbentbody. It is also common to have absorbent bodies comprising layers ofdifferent material with different properties with respect to liquidreceiving capacity, liquid distribution capacity and storage capacity.The thin absorbent bodies, which are common in for example baby diapersand incontinence guards, often comprise a compressed mixed or layeredstructure of cellulosic fluff pulp and superabsorbent. The size andabsorbent capacity of the absorbent core may be varied to be suited fordifferent uses such as for infants or for incontinent adults.

Pant Diaper

The pant diaper disclosed in FIG. 1 is intended to enclose the lowerpart of the wearer's trunk like a pair of absorbent pants. It comprisesa core region 3 located in the narrow crotch portion 19 of the articleand extending into the front 5 and back regions 6 of the absorbentpants. A chassis region 4 surrounds the core region 3. The core region 3is defined as the surface area of the article which is occupied by theabsorbent core 2 and the areas outside the core which are covered by theliquid-impervious backsheet 9. The chassis 4 comprises front 5, back 6and waist regions 7 located outside the crotch region 3. The front 5 andback regions 6 are joined to each other along their longitudinal edgesby ultrasonic welds 15, glue strings or the like.

According to one embodiment of the invention the surface area of theabsorbent core 2 amounts to no more than 30% of the total surface areaof the article, preferably no more than 20%, as measured in a flat stateof the article. The term “flat state” herein means in an openeduntensioned state, as seen in FIG. 2, and in which any tensioned elasticmembers have been deactivated.

The elastic web material 11 may cover the entire article, including thecore region 3 and the entire chassis region 4. However according to apreferred embodiment a substantial part of the crotch portion 19 of thearticle is free from the elastic web material 11. A “substantial part”used herein refers to at least 50%, preferably at least 75%. Preferablyalso the waist region 7 of the chassis region is free from the elasticweb material 11. The waist region 7 comprises a nonwoven material thatis elasticized by elastic members 14, such as elastic threads,contractably affixed between material layers, such as nonwovenmaterials. Such elastic members 14 may also be arranged around the legopenings of the article. Ultrasonic welds 16, glue strings or the like,join the elastic laminate 11 to the elasticized nonwoven in the waistregion 7.

The liquid-impervious backsheet material 9 underlies the absorbent core2 and adjacent areas immediately outside the absorbent core 2. The areacovered by the liquid-impervious backsheet 9 is defined as the coreregion 3. A nonwoven material 18 is arranged on the garment-facing sideof the liquid-impervious backsheet 9 in the crotch portion of thearticle. The nonwoven material 18 is joined to the elastic web material11 by means of ultrasonic welds 17, glue strings or the like. Theelastic web material 11 and the liquid impervious backsheet overlap inthe outer parts of the core region 3, as seen in FIG. 2, wherein theelastic web material 11 is arranged on the garment facing side of theliquid impervious backsheet 9.

The elastic web material 11 is preferably arranged as an outsidecoversheet material as well as inner coversheet material over at least asubstantial part of the front region 5 of the chassis 4, which duringuse is intended to be applied against the stomach of the wearer, exceptfor the waist region 7. A “substantial part” used herein means at least50% of the surface area, preferably at least 75%, of the surface area ofthe front region 5 of the chassis 4. It is further preferred that theelastic web material 11 is arranged as an outside coversheet material aswell as inner coversheet material over both the front 5 and back regions6 of the chassis 4. Thus no additional backsheet or topsheet materialsare required and the elastic web material constitutes the sole componentof in these parts of the chassis 4. In at least 20%, preferably at least25%, more preferably at least 30% and most preferably at least 40% ofthe total surface area of the article, as seen in a flat state accordingto FIG. 2, the elastic web material 11 constitutes the sole component ofthe chassis.

No additional elasticized side panels joining the front and back regions5 and 6 are needed when using the elastic web material 11 according tothe invention. If desired, additional elasticized side panels may ofcourse be provided, especially in cases where the elastic web material11 is arranged only in parts of the front and/or back regions.

As stated above the elastic web material 11 has an opacity of at least40%, preferably at least 50% and more preferably at least 60%.

The opacity of the elastic web material provides a cloth-like appearanceto the article, which is of particular importance when the article is apant diaper. Especially in this case, where the elastic web materialforms the sole component in considerable surface area regions of thepant diaper, such as large areas of the front and back regions, and theabsorbent core covers only relatively small areas, 30% or less, of thearticle, the appearance of the elastic web material is of greatimportance for the overall appearance of the article. Thus by making theelastic web material opaque with an opacity of at least 40%, the pantdiaper will appear more cloth-like and more like “normal” underwear,than if the elastic web material would have a higher degree oftransparency.

It is further desired that the elastic web material has a punctureresistance of at least 15N as measured according to ASTM DesignationD3763-02. Preferably, the elastic web material of the present inventionhas a puncture resistance of at least 20N, and more preferably at least30N.

The elastic web material should preferably have a softness according toKawabata of at least 20, preferably at least 30 and most preferably atleast 40.

It is further desired that it has a formability according to Kawabata ofno more than 50, preferably no more than 30, more preferably no morethan 20 and most preferably no more than 10.

It is also desired that the elastic web material has a drapabilityaccording to Kawabata of no more than 40.

Description of Test Methods

Opacity

The opacity of the elastic web material is measured according to aslightly modified version of SS-ISO 2471:1998 by Swedish StandardInstitute (Diffuse Reflectance Method). The method is originallyintended for measuring the opacity for paper sheets, but it alsofunctions well for measuring the opacity of other types of sheetmaterials, such as elastic laminates according to this invention. Theopacity is measured in an unstretched condition of the elastic webmaterial. The principle of the test method is to measure theSingle-Sheet Luminous Reflectance Factor, R₀, through a single sheetagainst a standardized black backing and the Intrinsic LuminousReflectance Factor, R_(∞), against a completely opaque white backing.The opacity (%) is calculated from the formula 100·R₀/R_(∞).

The following modifications of the test method were made:

-   -   i) When measuring the Single-Sheet Luminous Reflectance Factor,        R₀, a black velvet fabric was used as backing.    -   ii) When measuring the Intrinsic Luminous Reflectance Factor,        R_(∞), the measurement was made on one single sheet of the        elastic laminate against a white tile as backing.    -   iii) The CIE illuminant D65 (10°) was used instead of the CIE        illuminant C) (2°).

The measured opacity values are mean values from five measurements.

Puncture Strength

Puncture strength is measured according to ASTM Designation D3763-02.From penetration impact-type tests, this method produces data of loadversus displacement. The maximum load for each laminate is calculated.

Tensile strength (Reference: ASTM D 882)

The method measures tensile strength and elongation of differenceelastic materials. The tensile strength and elongation of a well-definedtest piece is tested by means of a tensile tester.

Apparatus: Instron 4301

-   -   Tensile tester connected to a computer    -   Crosshead speed: 500 mm/min    -   Clamp distance: 50 mm

Sample preparation: Test samples are cut from the entire width of thematerial. The width of the sample shall be 25.4 mm and the length atleast 50 mm longer than the clamp distance if possible. It is ofimportance that the edges of the sample are even and without breaknotches. The samples are conditioned for at least 4 h in 50% RH±5% RHand 23° C.±2° C. before testing.

Procedure: The tensile tester is calibrated according to the apparatusinstructions and set to zero. The sample is mounted and it is ensuredthat it is not obliquely or unevenly fastened. The material is preventedfrom slipping by using clamps covered with galloon or similar material.The tensile tester is started, and stopped after the material has broken(if not automatically controlled). Measurements resulting from prematurefailures (i.e. the sample breaks at the clamp, or is damaged duringpreparation) are ignored if possible.

The following results are expressed by the tensile tester/computer:

-   -   Maximum force, N/25.4 mm    -   Elongation at maximum force, %    -   Break force, N/25.4 mm    -   Elongation at break force, %    -   Knee point, N/%

Elasticity Test

The method measures how an elastic material behaves at repeated load andunload cycles. The sample is stretched to a predetermined elongation anda cyclic movement between 0 and said predetermined elongation isperformed. Desired load and unload forces are recorded. The permanent,i.e. remaining, elongation of the relaxed material is measured.

A tensile tester, Lloyd LRX, able to perform cyclic movements andequipped with a printer/plotter or software presentation is used. Thesample is prepared by cutting it to a width of 25 mm and a length thatis preferably 20 mm longer than the distance between the clamps in thetensile tester.

The tensile tester is calibrated according to the apparatusinstructions. The parameters needed for the test (load and unloadforces) are adjusted to:

-   -   Crosshead speed: 500 mm/min    -   Clamp distance: 50 mm    -   Preload: 0.05 N

The sample is placed in the clamps according to the marks and it is madesure that the sample is centred and fastened perpendicularly in theclamps. The tensile tester is started and three cycles between 0 and thepredetermined elongation, equal to the highest defined 1^(st) load, areperformed. Before the last cycle, the sample is relaxed for 1 minute,then the permanent elongation is measured by stretching the sample untila force of 0.1 N is detected and the elongation is read.

The permanent elongation after relaxation should be less than 10% and ismeasured by the method above. Thus an elasticity of 30% is defined asthat the laminate should have a permanent relaxation after elongation ofless than 10% after being exerted to an elongation of 30% in the tensiletester above. An elongation of 30% means an elongation to a length thatis 30% longer than the initial length of the sample.

Kawabata Tests

The Kawabata KES-FB test is a Japanese quality judgment system used fortextile materials and is disclosed in “The Standardization and Analysisof Hand Evaluation (2nd Edition), Sueo Kawabata, July 1980, The HandEvaluation and Standardization Committee, The Textile Machinery Societyof Japan”. The test used in this invention uses two of the Kawabatatesting machines, KES-FB2 for measuring Bending rigidity, B (gf·cm²/cm),and KES-FB1 for measuring Shear stiffness, G (gf/cm·degree) and Tensilestrain, EMT (%).

Bending Rigidity (B) KES-FB2

The slope was measured between 0.5 cm⁻¹ and 1.5 cm⁻¹ and −0.5 cm⁻¹ and−1.5 cm⁻¹.

The measurements were performed in both directions (MD and CD) with thefollowing settings:

Total sample area: 20×20 cm;

Maximum curvature: Kmax=±2.5 cm⁻¹;

Bending rate: 0.5 cm⁻¹/sec;

Sample effective dimension: 20 cm length and 1 cm width;

Bending deformation is applied to the width direction.

Shear Stiffness (G) KES-FB1

The slope was measured between 0.5 cm⁻¹ and 2.5 cm⁻¹ and −0.5 cm⁻¹ and−2.5 cm⁻¹.

The measurements were performed in both directions (MD and CD) with thefollowing settings:

Total sample area: 20×20 cm;

Tension of specimen: W=W=10 gf/cm;

Maximum shear angle: σ=±8°.

Sample effective dimension: 20 cm width and 5 cm length;

Shear deformation is applied to the width direction.

Tensile Strain (EMT)

The measurements were performed in both directions (MD and CD) with thefollowing settings:

Total sample area: 20×20 cm;

Maximum load: Fm=500 gf/cm;

Tensile speed: 0.2 mm/sec.

Sample effective dimension: 20 cm width and 2.5 cm length;

Tensile deformation is applied to the length direction.

Elongation sens 50 mm/10V.

Softness (S)

The Softness (S) according to Kawabata is obtained from the formula:

S=√{square root over (EMT/B)}

Formability (F)

The Formability (F) according to Kawabata is obtained from the formula:

F=B·EMT.

Drapability (D)

The Drapability (D) according to Kawabata is obtained from the formula:

D=116+25·log(B·G/W), wherein W is the basis weight of the sample.

EXAMPLE

Opacity

The opacity of an elastic laminate sample was measured. The sample wasan elastic laminate according to the invention comprising an innerapertured three-layer elastic film of PE-SEBS-PE, basis weight 36 g/m²and two outer layers of spunbond material, PP (polypropylene), eachhaving a basis weight of 22 g/m². The laminate is produced by a modifiedversion of the method disclosed in WO 03/04788 and which is describedabove, wherein one spunbond layer is applied to the film in a tackystate and will thus bond to the film layer, while the other spunbondlayer is adhesively laminated to the film layer using for example apressure sensitive hot melt adhesive (glue amount 3 g/m²). The laminateis incrementally stretched, at which the non-elastic spunbond layers arestretched to a point below the elongation at maximum load to retain somestrength in the spunbond layers. The elasticity of the laminate afterstretching is close to the elasticity of the elastic film layer.

The above-mentioned basis weights of the layers refer to the finishedlaminate after stretching. Before stretching the basis weight of theindividual layers were: inner film layer 40 g/m², outer spunbond layers25 g/m² each and glue layer 3 g/m². Since it is difficult to measure thebasis weights of the individual layers after lamination and stretchingan approximation has been made from the basis weights of the layersbefore lamination and stretching. The laminate before stretching had atotal basis weight before stretching of 93 g/m² and after stretching ithad a basis weight of 85 g/m², which means a deformation of about 10%.It is then assumed that the deformation of the individual fibrous layersand the film layer is the same, i.e. about 10%.

The inner film layer contained 4.9% by weight filler in the form ofTiO₂. The open area of the film layer was 13%.

The opacity of the laminate was about 68%.

An opacity value of at least 40% is acceptable in order to provide thedesired cloth-like appearance of the pant diaper disclosed above, whichin considerable areas of the chassis contains the elastic laminate asthe sole component. Preferably the opacity should be at least 50%, morepreferably at least 60%.

It is further desired, for example for cost reasons, to have a low basisweight of the elastic laminate. The basis weight should be 100 g/m² orlower. The ratio Opacity/Basis Weight is therefore also an aspect ofthis invention. Preferably this ratio should be at least 0.4, morepreferably at least 0.5 and most preferably at least 0.6, whereinopacity is measured in % and the basis weight is measured in g/m².

Puncture Resistance

The puncture resistance of three different samples (A, B and C) weremeasured according to ASTM Designation D3763-02 and are shown in Table1.

Tensile Strength

The puncture resistance of three different samples (A, B and C) weremeasured according to the method given above and are shown in Table 1.

Elasticity

The elasticity of three different samples (A, B and C) were measuredaccording to the method given above and are shown in Table 1.

Sample A is an elastic laminate according to WO03/047488 with 15 g/m² PPspunbond nonwoven on both sides of a 40 gsm elastic film. The usedspunbond nonwoven has an elongation at maximum load of 60%, which isless than the elasticity of the laminate. The low puncture resistance ofthis material means that it falls outside the preferred values claimedin this application.

Sample B is an elastic laminate with 25 g/m² PP/PE spunbond nonwoven onboth sides of a 36 g/m² elastic film.

Sample C is an elastic laminate with one layer of 25 g/m² PP/PE nonwovenand one layer of 20 g/m² PP/PE nonwoven on opposite sides of a 36 g/m²elastic film.

TABLE 1 Sample Sample Sample A B C Puncture force (N) 12.8 49.5 40.6Basis weight (g/m²) 78.66 87.96 82.71 Tensile strength and Elongation MD(machine direction) Tensile strength at Peak (MD), N/25 mm 8.29 25.328.03 Elongation at break, % 269.82 311.94 691.47 Elongation atPeak/Deformation, % 136 111.44 109.28 CD (cross direction) Tensilestrength at Peak (CD), N/25 mm 11.72 11.15 9.16 Elongation at break, %792.87 768.19 160.15 Elongation at Peak/Deformation, % 74.88 124.82134.42 Determination of load & unload forces and permanent elongationTensile strength at 80% elongation (1^(st) 2.78 7.11 10.66 cycle)Permanent Elongation (3^(rd) cycle) 7.86 7.52 8.09 3^(rd) RetractionForces At 80%, N/25 mm 1.14 1.44 1.42 At 60%, N/25 mm 0.82 0.85 0.8 At40%, N/25 mm 0.54 0.53 0.48

Kawabata Tests

Four different samples were measured in a Kawabata test with respect toBending rigidity (B), Shear stiffness (G) and Tensile strain (EMT). Fromthese measured values the Softness (S), Formability (F) and Drapability(D) were calculated.

The four samples were:

Sample laminate (SL): an elastic laminate as disclosed with respect tothe Opacity test above.

Ref. 1: Cotton-knitted goods, so called jersey with elastic threads.

Ref. 2: Outer coversheet of Tena Discreet incontinence pant (odourcontrol, size medium) produced by SCA Hygiene Products AB. The outercoversheet comprises two layers of nonwoven with parallel elasticthreads there between, which wrinkle the material.

Ref. 3: Outer coversheet material of Poise normal super incontinencepant produced by Kimberly-Clark. The outer coversheet comprises twolayers of nonwoven with parallel elastic threads there between whichwrinkle the material.

A climate conditioning of the materials were performed at 20° C. and 65%RH for 48 hours. For the pant products, the absorbent core was removedand the outer coversheet was stretched over a knitwear measuring devicefor 24 hours and was then allowed to relax in the same climate during 24hours.

The sizes of the samples were 10×10 cm.

All tests were made on three samples and in two material directions(machine direction, MD, and cross direction, CD).

The following results were obtained.

TABLE 2 B, Bending rigidity G, Shear stiffness (gf · cm²/cm) (gf/cm ·degree) EMT, Tensile strain (%) Sample MD CD Mean MD CD Mean MD CD MeanSL 0.095 0.022 0.059 1.46 1.38 1.42 208.4 92.0 150.2 Ref. 1 0.03 0.030.03 0.58 0.64 0.61 160.6 173.2 166.9 Ref. 2 1.05 0.09 0.57 0.87 0.680.77 23.9 211.7 117.8 Ref. 3 1.53 0.04 0.78 1.74 1.21 1.47 26.28 195.3110.8

From these results the Softness (S), the Drapability (D) and theFormability (F) according to Kawabata were calculated according to theformulas stated above. These results are stated in Table 3 below.

TABLE 3 Drapability (D) Basis Softness (S) 116 + 25 log Formability (F)Weight (W) Sample {square root over (EMT/B)} (B · G/W) B · EMT g/m² SL50 40 9 88 Ref. 1 75 13 5 231 Ref. 2 14 45 67 160 Ref. 3 12 51 87 133

The results should be interpreted in the following way:

Softness (S): a higher value indicates a softer material.

Drapability (D): a higher value indicates a stiffer material.

Formability (F): a higher value indicates that the material is lessformable.

The test laminate according to the invention has a Softness (S) and aFormability (F) according to Kawabata which is close to cotton-knittedgoods (Ref. 1). Also the Drapability (D) according to Kawabata is closerto the cotton-knitted reference material than the other two testedmaterials, used as outer coversheets on conventional incontinence pants.Thus the use of the elastic laminate as outer coversheet material in atleast a part of the chassis region of the absorbent pant provides a pantarticle having a cloth-like feeling close to a cotton material. The pantwill also have an excellent comfort and fit to the wearer's body. Byusing the elastic laminate only in those parts of the pant in which theproperties of the material is best utilized, a very economic utilizationof the material is accomplished.

As described above it is further understood that other types of elasticweb materials, than the laminate described above, may be used, such aselastic nonwoven materials, nonwoven materials which per se areinelastic, but which have been elastified by means of elastic threadsetc. The elastic web materials may comprise one layer or two or morelayers that have been laminated.

1. A pant type absorbent article, said article comprising a core regionwith an absorbent core and a chassis surrounding the core region, saidchassis comprising front, back and waist regions, while the core regionis located at least in a crotch portion of the article, a liquidimpermeable backsheet is arranged at least in the core region on thegarment-facing side of the absorbent core and a liquid permeabletopsheet is arranged at least in the core region on the wearer-facingside of the absorbent core, said article having a longitudinal and atransverse direction, said article in at least a part of the chassisregion comprises an outer coversheet in the form of an elastic webmaterial constituting the sole component of the chassis in at least 20%of the total surface area of the article, said elastic web materialhaving an opacity of at least 40% and a basis weight of no more than 100g/m².
 2. The absorbent article as claimed in claim 1, said elastic webmaterial has an opacity of at least 50%.
 3. The absorbent article asclaimed in claim 1, wherein the elastic web material is a laminatecomposed of first and second layers of fibrous material and an elasticfilm layer located between said first and second fibrous layers.
 4. Theabsorbent article as claimed in claim 3, wherein said elastic film layercontains an opacifying filler.
 5. The absorbent article as claimed inclaim 4, wherein the opacifying filler is selected from the group:organic and inorganic dyes, colouring agents and whitening agents. 6.The absorbent article as claimed in claim 4, wherein the opacifyingfiller is selected from the following group of substances: titaniumdioxide, inorganic carbonates, synthetic carbonates, talc, nephelinesyenite, magnesium hydroxide, aluminium trihydrate siatomaceous earth,mica, natural or synthetic silicas, calcinated clays and mixturesthereof.
 7. The absorbent article as claimed in claim 3, wherein atleast one of the layers of fibrous material has an elongation at maximumload greater than the elasticity of the elastic laminate.
 8. Theabsorbent article as claimed in claim 7, wherein both layers of fibrousmaterial have an elongation at maximum load greater than the elasticityof the elastic laminate.
 9. The absorbent article as claimed in claim 7mwherein at least one of the layers of fibrous material have anelongation at maximum load of at least 10% greater than the elasticityof the elastic laminate.
 10. The absorbent article as claimed in claim3, wherein said elastic film layer is breathable.
 11. The absorbentarticle as claimed in claim 10, wherein said elastic laminate has aWater Vapour Transmission Rate according to ASTM E96-00 Procedure D ofat least 1500 g/m² 24 h.
 12. The absorbent article as claimed in claim10, wherein the elastic film layer has an open area of at least 5%. 13.The absorbent article as claimed in claim 3, wherein the first and/orthe second layers of fibrous material comprise a mixture ofpolypropylene and polyethylene polymers.
 14. The absorbent article asclaimed in claim 3, wherein said elastic laminate comprises first andsecond fibrous layers of spunbond material, each having a basis weightof between 10 and 35 g/m², and a breathable elastic film layer having abasis weight between 20 and 80 g/m², said elastic laminate having aWater Vapour Transmission Rate according to ASTM E96-00 Procedure D ofat least 1500 g/m² 24 h.
 15. The absorbent article as claimed in claim1, wherein the elastic web material has a basis weight of no more than90 g/m².
 16. The absorbent article as claimed in claim 1, wherein theelastic web material has an opacity (%)/basis weight (g/m²) ratio of atleast 0.4.
 17. The absorbent article as claimed in claim 1, the elasticweb material constitutes the sole component of the chassis in at least25% of the total surface area of the article.
 18. The absorbent articleas claimed in claim 1, said elastic web material has an elasticity inthe transverse direction of the article of at least 30% when measuredaccording to the elasticity test specified in the description.
 19. Theabsorbent article as claimed in claim 18, wherein the elastic webmaterial has an elasticity in the longitudinal direction of the articleof at least 20% when measured according to the elasticity test specifiedin the description.
 20. The absorbent article as claimed in claim 1,wherein said elastic web material has Softness (S) according to Kawabataof at least
 20. 21. The absorbent article as claimed in claim 1, whereinsaid elastic web material has a Formability (F) according to Kawabata ofno more than
 50. 22. The absorbent article as claimed in claim 1,wherein said elastic web material has a Drapability (D) according toKawabata of no more than
 40. 23. The absorbent article as claimed inclaim 1, wherein a part of the crotch portion of the article is freefrom said elastic web material.
 24. The absorbent article as claimed inclaim 1, wherein the waist region of the chassis is free from saidelastic web material.
 25. The absorbent article as claimed in claim 1,wherein the surface area of the absorbent core amounts to no more than30% of the total surface area of the article, as measured in a flatstate of the article.
 26. The absorbent article as claimed in claim 1,wherein the article is a pull-up pant product comprising an elasticizedwaist region, which is free from said elastic web material, a crotchportion which is also free from said elastic web material and whereinthe elastic web material is arranged as a sole component of the chassisin at least a substantial part of the front region of the article, whichin use is intended to be applied over the stomach of the wearer.
 27. Theabsorbent article as claimed in claim 7, wherein at least one of thelayers of fibrous material have an elongation at maximum load of atleast 20% greater than the elasticity of the elastic laminate.
 28. Theabsorbent article as claimed in claim 10, wherein said elastic laminatehas a Water Vapour Transmission Rate according to ASTM E96-00 ProcedureD of at least 3000 g/m² 24 h.
 29. The absorbent article as claimed inclaim 10, wherein the elastic film layer has an open area of at least8%.
 30. The absorbent article as claimed in claim 3, wherein saidelastic laminate comprises first and second fibrous layers of spunbondmaterial, each having a basis weight of between 15 and 25 g/m², and abreathable elastic film layer having a basis weight between 20 and 60g/m², said elastic laminate having a Water Vapour Transmission Rateaccording to ASTM E96-00 Procedure D of at least 3000 g/m² 24 h.
 31. Theabsorbent article as claimed in claim 1, wherein the elastic webmaterial has an opacity (%)/basis weight (g/m²) ratio of at least 0.6.32. The absorbent article as claimed in claim 1, the elastic webmaterial constitutes the sole component of the chassis in at least 40%of the total surface area of the article.
 33. The absorbent article asclaimed in claim 1, said elastic web material has an elasticity in thetransverse direction of the article of at least 70% when measuredaccording to the elasticity test specified in the description.
 34. Theabsorbent article as claimed in claim 1, wherein said elastic webmaterial has Softness (S) according to Kawabata of at least
 40. 35. Theabsorbent article as claimed in claim 1, wherein said elastic webmaterial has a Formability (F) according to Kawabata of no more than 20.36. A pant type absorbent article, said article comprising: a coreregion with an absorbent core and a chassis surrounding the core region,said chassis comprising front, back and waist regions, while the coreregion is located at least in a crotch portion of the article, a liquidimpermeable backsheet is arranged at least in the core region on thegarment-facing side of the absorbent core, and a liquid permeabletopsheet is arranged at least in the core region on the wearer-facingside of the absorbent core, said article having a longitudinal and atransverse direction, said article in at least a part of the chassisregion comprises an outer coversheet in the form of an elastic webmaterial in at least 20% of the total surface area of the article, saidelastic web material having an opacity (%) to basis weight (g/m²) ratioof at least 0.4.
 37. A pant type absorbent article, said articlecomprising: a core region with an absorbent core and a chassissurrounding the core region, said chassis comprising front, back andwaist regions, while the core region is located at least in a crotchportion of the article, a liquid impermeable backsheet is arranged atleast in the core region on the garment-facing side of the absorbentcore, and a liquid permeable topsheet is arranged at least in the coreregion on the wearer-facing side of the absorbent core, said articlehaving a longitudinal and a transverse direction, said article in atleast a part of the chassis region comprises an outer coversheet in theform of an elastic web laminate material in at least 20% of the totalsurface area of the article, said elastic web laminate material having alayer of apertured elastic film having a basis weight between 20 and 80g/m², and an opacity (%) to basis weight (g/m²) ratio of at least 0.4.38. The absorbent article as claimed in claim 37, wherein said aperturedelastic film has an open area of at least 5%.
 39. A pant type absorbentarticle, said article comprising: a core region with an absorbent coreand a chassis surrounding the core region, said chassis comprisingfront, back and waist regions, while the core region is located at leastin a crotch portion of the article, a liquid impermeable backsheet isarranged at least in the core region on the garment-facing side of theabsorbent core, and a liquid permeable topsheet is arranged at least inthe core region on the wearer-facing side of the absorbent core, saidarticle having a longitudinal and a transverse direction, said chassisregion including an outer coversheet in the form of an elastic webmaterial in at least 20% of the total surface area of the article, saidelastic web material having an opacity of at least 40% and a WaterVapour Transmission Rate according to ASTM E96-00 Procedure D of atleast 1500 g/m² 24 h.